Medical practitioners, such as military medics, civilian emergency-medical personnel, nurses, and physicians, routinely perform vascular-access procedures (e.g., IV insertion, central venous-line placement, peripherally-inserted central catheter, etc). It is desirable for a practitioner to be proficient at performing these procedures since the proficient practitioner is far less likely to injure a patient and is almost certain to reduce the patient's level of discomfort.
Becoming proficient in vascular-access procedures requires practice. In fact, the certification and re-certification requirements of some states mandate a minimal number of needle sticks, etc., per year per provider. Historically, medical practitioners practiced needle-based procedures on live volunteers. More recently, simulation techniques and devices have been developed to provide training in vascular-access procedures without the use of live volunteers. U.S. Pat. No. 6,470,302 (“the '302 patent”) surveys the art of medical-simulation devices and also discloses a vascular-access simulation system.
The vascular-access simulation system that is disclosed in the '302 patent includes an “interface” device and a computer system. To practice a vascular-access procedure, a user manipulates an “instrument,” referred to in the patent as a “catheter unit assembly,” which extends from the device and serves as a catheter-needle. Potentiometers and encoders within the interface device track the motion and position of the instrument and relay this information to the computer system. The computer system performs a simulation of the surface and subsurface anatomy of human skin, and determines the effect of the instrument's motion on the skin's anatomy. Simulated results are displayed by the computer system. Using the motion information from the interface device, the computer system also generates a control signal that controls a force-feedback system that is coupled to the instrument. The force-feedback system generates various resistive or reactive forces that are intended to simulate the forces that are experienced by a medical practitioner during an actual vascular-access procedure. The user senses these forces during manipulation of the instrument.
The system that is disclosed in the '302 patent has many shortcomings that substantially limit its utility as a training or accreditation tool. In particular, among other drawbacks, the system that is disclosed in the '302 patent provides only a limited ability to practice and realistically mimic certain skin-interaction techniques that are an important part of vascular-access procedures. These skin-interaction techniques include “palpation,” “skin stretch,” and “occlusion.”
Palpation is a multi-purpose technique. It can be used by a practitioner to locate hidden veins. Veins might not be readily locatable due to the advanced age or poor physical condition of the patient, the procedure being performed, or due to other reasons. To palpate for hidden veins, the practitioner pats the skin. Palpation can also be used to obtain information about a candidate vein once it has been located. In particular, the practitioner can determine whether the candidate vein is sufficiently engorged. A practitioner can also determine, via palpation, whether a vein is sufficiently straight (at an intended insertion point) for catheterization. To palpate a vein to obtain this type of information, the practitioner moves one or two fingers lightly over the candidate vein.
Occlusion is a technique that is performed during catheterization. Specifically, a finger or thumb of the non-dominant hand is used to apply pressure on the catheter at the insertion point so that no blood leaks out of the hub of the catheter when the stylet is removed. To practice the third technique mentioned above—the skin-stretch technique—the thumb of the non-dominant hand pulls a patient's skin, rendering it taut. This reduces a patient's level of discomfort and anchors the vein so that it doesn't move during angiocatheter insertion.
Of these three skin-interaction techniques, only the “skin stretch” can be practiced using the device that is disclosed in the '302 patent. And the mechanism that is responsible for skin stretch has a limited ability to realistically simulate this procedure. In particular, the “skin” on which the skin stretch technique is practiced is a belt—a “mock” skin—that bears little resemblance to real skin. A resilient backing is disposed beneath the belt to simulate the resiliency of skin. (See, col. 10, lines 49+.) Furthermore, the module on which the skin-stretch technique is practiced resides within a casing that is attached to and separate from the housing in which the needle-insertion procedure is practiced. This structural arrangement does nothing to promote a user's “suspension of disbelief.” That is, it is clear that the technique is being performed on a machine that is not the least bit suggestive of human anatomy.
The inability to practice and realistically simulate these skin-interaction techniques limits the utility of prior-art vascular-access simulation systems for use as a training or accreditation tool.